Some electrotherapy apparatuses used to perform electrotherapy dynamically control the electrotherapy waveform applied to the patient in response to real time impedance measurements made upon the patient. Hardware implementations of these electrotherapy apparatuses measure such parameters as the charge delivered to the patient or the voltage of the electrotherapy waveform applied to the patient to estimate the impedance. In response to these measurements, the electrotherapy apparatuses adjust the electrotherapy waveform delivered to the patient to improve the effectiveness of the electrotherapy.
Electrotherapy apparatuses that dynamically control the electrotherapy waveform applied to the patient have implemented threshold comparison functions in hardware. The hardware has included such things as comparators using voltage references to determine when a measured parameter has reached a threshold value. A cost savings and a reliability improvement could be realized if the hardware required for implementing the threshold comparison could be simplified. A need exists for an electrotherapy apparatus having reduced hardware complexity.